Emergency landing gear cabin door strength design method

Abstract

The invention belongs to the field of aircraft strength design, and particularly relates to an emergency landing gear cabin door strength design method, which comprises the following steps of: acquiring a cabin door impact point of a landing gear and a landing rack cabin door when the landing gear is put down under the condition of a landing gear cabin door fault; calculating a first load of the undercarriage to the impact point according to the gravity of the undercarriage and the position of the impact point; on the basis of the first load, a second load of the preset damage position is calculated in combination with the geometrical relationship between the impact point and the undercarriage cabin door; based on the second load and a design limit load of a preset damage position, a structure damage load of the preset damage position is calculated, and the structure damage load is larger than the design limit load and smaller than the second load; and the structural strength of the preset damage position is designed according to the structural damage load.

Description

Technical Field

[0001] The present application belongs to the field of aircraft strength design, and in particular relates to a strength design method for an emergency landing gear door. Background Art

[0002] The landing gear door is a major component of the aircraft, and its opening and closing functions are generally achieved through the door upper lock and the actuator. Under normal circumstances, when the aircraft returns, the door upper lock is unlocked, the actuator is lowered, the door is opened, and the landing gear is lowered. During the entire process, both the upper lock unlocking and the actuator lowering may fail, resulting in the door being unable to open and the aircraft being unable to return normally. Summary of the invention

[0003] In order to solve the above problems, the present application provides a strength design method for an emergency landing gear door, comprising:

[0004] Get the impact point between the landing gear and the landing gear door when the landing gear is lowered in the case of a landing gear door failure;

[0005] Calculating the first load of the landing gear on the impact point according to the gravity of the landing gear, the hydraulic load of the retraction and extension actuator, and the position of the impact point;

[0006] Based on the first load and in combination with the geometric relationship between the impact point and the landing gear door, a second load at a preset damage position is calculated;

[0007] Based on the second load and the design limit load of the preset failure position, a structural failure load at the preset failure position is calculated, wherein the structural failure load is greater than the design limit load and less than the second load;

[0008] The structural strength of the preset failure position is designed according to the structural failure load.

[0009] Preferably, the first end of the door is hinged to the fuselage, the middle part of the door is hinged to the actuating mechanism, the actuating mechanism drives the door to rotate around the first end, and the preset destruction position is arranged at the hinge between the actuating mechanism and the door.

[0010] Preferably, when the actuating mechanism is hinged to the hatch by bolts, the bolts are used as breaking parts, and the structural breaking load is equal to K times the shear breaking load of the bolts, and the shear breaking load of the bolts is obtained by a shear breaking test.

[0011] Preferably, the structural failure load is equal to the structural design bearing capacity×K, and the K value is between 1.5 and 1.8.

[0012] Preferably, the structural failure load is K times the structural design bearing capacity multiplied by a safety margin factor.

[0013] Preferably, a functional relationship between different opening positions of the landing gear and the second loads received at the preset damage position is constructed; and the structural damage load is less than the minimum second load value.

[0014] Preferably, the second load received by the landing gear at the preset damage position when the landing gear hits the door is calculated by the following functional relationship;

[0015] M T =M F =M G +M P

[0016] in:

[0017] M G is the moment of the landing gear inertia load on the support arm;

[0018] M P The moment of the hydraulic load of the landing gear retraction and extension actuator on the support arm;

[0019] M F is the moment of the impact point load on the door rocker arm;

[0020] M T It is the moment of the door actuator connection point load on the door rocker arm.

[0021] The advantages of this application include: the connection structure between the landing gear door actuator and the door support is designed as a weak part through reasonable strength design, and its damage load is between the normal flight load and the reaction load of the impact, and the impact of the landing gear is used to achieve emergency release of the door. The solution is simple to implement, with high reliability, easy replacement of the damaged structure, and lower maintenance cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the landing gear door structure of a preferred embodiment of the present application;

[0023] Figure 2 The failure shear force and standard value of different batches of a bolt;

[0024] Figure 3 It is a schematic diagram of the relationship between the bolt failure shear force and the design bearing capacity. DETAILED DESCRIPTION

[0025] In order to make the technical solution and advantages of the present application clearer, the technical solution of the present application will be further described in detail in detail and in detail in conjunction with the accompanying drawings. It can be understood that the specific embodiments described here are only partial embodiments of the present application, which are only used to explain the present application, not to limit the present application. It should be noted that, for the convenience of description, only the parts related to the present application are shown in the accompanying drawings, and other related parts can refer to the general design. In the absence of conflict, the embodiments in the present application and the technical features in the embodiments can be combined with each other to obtain new embodiments.

[0026] In addition, it should be noted that, unless otherwise clearly specified and limited, the words "installed", "connected", "connected" and similar terms used in the description of this application should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, an indirect connection through an intermediate medium, or the internal connection of two components. Technical personnel in the field can understand their specific meanings in this application according to the specific circumstances.

[0027] like Figure 1 As shown, in the event of a fault, the retraction and extension logic is changed, and the landing gear is directly lowered alone after the cabin door is opened, and the landing gear is used to hit the cabin door to achieve emergency opening of the cabin door. The design of this emergency plan must not only ensure that the structure is intact during normal flight, but also ensure that the damage range during impact is as small as possible and the damaged structure is easy to replace.

[0028] The present application designs the strength of the weak link of the door actuator cylinder, thereby realizing the emergency release of the landing gear door. The present application provides a strength design method for the emergency release of the landing gear door, including:

[0029] Get the impact point between the landing gear and the landing gear door when the landing gear is lowered in the case of a landing gear door failure;

[0030] Calculating the first load of the landing gear on the impact point according to the gravity of the landing gear, the hydraulic load of the retraction and extension actuator, and the position of the impact point;

[0031] Based on the first load and in combination with the geometric relationship between the impact point and the landing gear door, a second load at a preset damage position is calculated;

[0032] Based on the second load and the design limit load of the preset failure position, a structural failure load at the preset failure position is calculated, wherein the structural failure load is greater than the design limit load and less than the second load;

[0033] like:

[0034]

[0035] The structural strength of the preset failure position is designed according to the structural failure load.

[0036] Preferably, the first end of the door is hinged to the fuselage, the middle part of the door is hinged to the actuating mechanism, the actuating mechanism drives the door to rotate around the first end, and the preset destruction position is arranged at the hinge between the actuating mechanism and the door.

[0037] Preferably, when the actuating mechanism is hinged to the hatch by bolts, the bolts are used as breaking parts, and the structural breaking load is equal to K times the shear breaking load of the bolts, and the shear breaking load of the bolts is obtained by a shear breaking test.

[0038] Preferably, where structural failure load = structural design bearing capacity × K, see Figure 2 , which shows the data of shear failure tests of bolts of different materials and batches. In the normal design process, the design bearing capacity of the bolts is used, that is, the standard value. The failure load obtained by the failure test needs to be multiplied by a coefficient K, and the K value is between 1.5 and 1.8.

[0039] See Figure 3 As shown, when designing for structural destruction, the destruction load must take into account a coefficient K on the basis of the safety margin. The K is determined based on the original data of the material or fastener bearing capacity test, and generally the value is not less than 1.5.

[0040] Preferably, a functional relationship between different opening positions of the landing gear and the second loads received at the preset damage position is constructed; and the structural damage load is less than the minimum second load value.

[0041] Preferably, the second load received by the landing gear at the preset damage position when the landing gear hits the door is calculated by the following functional relationship;

[0042] M T =M F =M G +M P

[0043] in:

[0044] M G is the moment of the landing gear inertia load on the support arm;

[0045] M P The moment of the hydraulic load of the landing gear retraction and extension actuator on the support arm;

[0046] M F is the moment of the impact point load on the door rocker arm;

[0047] M T It is the moment of the door actuator connection point load on the door rocker arm.

[0048] The advantages of this application include: the connection structure between the landing gear door actuator and the door support is designed as a weak part through reasonable strength design, and its damage load is between the normal flight load and the reaction load of the impact, and the impact of the landing gear is used to achieve emergency release of the door. The solution is simple to implement, with high reliability, easy replacement of the damaged structure, and lower maintenance cost.

[0049] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A strength design method for emergency landing gear door, characterized in that: include: Get the impact point between the landing gear and the landing gear door when the landing gear is lowered in the case of a landing gear door failure; Calculating the first load of the landing gear on the impact point according to the gravity of the landing gear, the hydraulic load of the retraction and extension actuator, and the position of the impact point; Based on the first load and in combination with the geometric relationship between the impact point and the landing gear door, a second load at a preset damage position is calculated; Based on the second load and the design limit load of the preset failure position, a structural failure load at the preset failure position is calculated, wherein the structural failure load is greater than the design limit load and less than the second load; The structural strength of the preset failure position is designed according to the structural failure load.

2. The strength design method for emergency landing gear door according to claim 1, characterized in that: The first end of the door is hinged on the fuselage, the middle part of the door is hinged to the actuating mechanism, the actuating mechanism drives the door to rotate around the first end, and the preset destruction position is set at the hinge between the actuating mechanism and the door.

3. The strength design method for emergency landing gear door according to claim 1, characterized in that: When the actuating mechanism is hinged to the hatch by bolts, the bolts are used as failure parts, and the structural failure load is equal to K times the shear failure load of the bolts, and the shear failure load of the bolts is obtained through a shear failure test.

4. The strength design method for emergency landing gear door according to claim 1, characterized in that: The structural failure load is equal to the structural design bearing capacity×K, and the K value is between 1.5 and 1.

8.

5. The strength design method for emergency landing gear door according to claim 4, characterized in that: The structural failure load is K times the structural design bearing capacity multiplied by a safety margin factor.

6. The strength design method for emergency landing gear door according to claim 1, characterized in that: A functional relationship between different opening positions of the landing gear and the second loads received at the preset damage position is constructed; the structural damage load is less than the minimum second load value.

7. The strength design method for emergency landing gear door according to claim 1, characterized in that: The second load on the landing gear when it hits the door and the preset damage position is calculated by the following functional relationship: M T =M F =M G +M P ; in: M G is the moment of the landing gear inertia load on the support arm; M P The moment of the hydraulic load of the landing gear retraction and extension actuator on the support arm; M F is the moment of the impact point load on the door rocker arm; M T It is the moment of the door actuator connection point load on the door rocker arm.

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